You seem to have it in your head that DPS is the only way to generate enmity, or at least, that's what your overall stance tells me. The common thought is that "PLD can't DPS, therefore it can't be a tank." The correct answer is "PLD can generate more than enough enmity through it's actions that DDs don't have to hold back and have enough survivability in a lot of situations to allow an extra DPS over a second WHM."

They're two distinct tanking styles right now. A WAR's tanking style is based more around generating enmity through it's own (and with Collusion, other's) damage at the cost of less defensive power. A PLD has a much higher enmity ceiling and more survivability post 1.22a but at the cost of less overall DPS from itself. There are pros and cons to each, now. Several LS and players have more than proven post update that current content, even speed runs, can be achieved with a PLD and a WAR tank.

While the jobs could probably use a little tweaking, there are very few instances where I'd take a PLD over a WAR and vice versa right now.